The invention concerns a process for the production of a pearl shine pigment preparation as a pre-product for a printing ink containing pearl shine pigment.
Pearl shine pigment is usually on the market in dust or powder form. For processing in the printing ink, the pearl shine pigment is mixed with a binding agent solution and possibly additives which are conventional in printing procedures and the mixture is adjusted to the viscosity required for application by a printing process. To achieve the soft shine effect which is typical of pearl shine pigment in the printing ink the distribution and orientation of the pearl shine pigment particles in the binding agent need to be as uniform as possible.
In principle high shearing forces are to be avoided in any procedure for processing pearl shine pigments. Therefore the pearl shine pigment must be subjected to pre-treatment with solvent over several hours (so-called "sumping") prior to the actual dispersing procedure for production of the printing ink. That operation is time-consuming and therefore also expensive. In spite of the pretreatment by "sumping" and agitation the desired uniform dispersion cannot always be achieved and as a result the printing may also not be fully satisfactory.